Neurotoxicity of organic solvents--recent findings

Author(s):Matsuoka M

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In this review,the recent findings of central nervous system (CNS) or peripheral nervous system (PNS) dysfunction induced by occupational exposure to organic solvents are described. While acute,high-level exposure to almost all organic solvents causes the general,nonspecific depression of CNS,it is still not clear whether chronic,low-level occupational exposure causes the chronic neurological dysfunction which has been called "organic solvent syndrome","painters syndrome","psycho-organic syndrome" or "chronic solvent encephalopathy". At least at lower than occupational exposure limits,chronic and low-level organic solvent exposure does not appear to cause the "symptomatic" neurological dysfunction. The chronic,moderate- to high-level exposure to a few organic solvents (such as carbon disulfide,n-hexane and methyl n-butyl ketone) affects CNS or PNS specifically. The substitutes for chlorofluorocarbons,2-bromopropane and 1-bromopropane were shown to have the peripheral nerve toxicity in the experimental animals. Shortly after these observations,human cases of 1-bromopropane intoxication with the dysfunction of CNS and PNS were reported in the United States. Neurological abnormalities in workers of a 1-bromopropane factory in China were also reported. Thus,the possible neurotoxicity of newly introduced substitutes for ozone-depleting solvents into the workplace must be considered. Enough evidences indicate that some common solvents (such as toluene and styrene) induce sensorineural hearing loss and acquired color vision disturbances in workers. In some studies using magnetic resonance imaging (MRI),cerebral atrophy,patchy periventricular hyperintensities and hypointensities in the basal ganglia were found in solvent-exposed workers as have been shown in toluene abusers (toluene leukoencephalopathy). Further studies using the neurobehavioral test batteries,neurophysiological measurements and advanced neuroimaging techniques are required to detect the "subclinical" dysfunction of nervous systems in workers exposed to organic solvents at low-level.